USB: Pack the usb_request_data struct.

We really should not be writing raw structs out to devices
for endianness' sake, but that's currently what *all* the
USB bus drivers do with this struct. So, add the _PACKED flag
to ensure it's always precisely 8 bytes.

Additionally, remove memory_chunk, as nothing uses it anymore.

src/add-ons/kernel/bus_managers/usb/usbspec_private.h

@@ -37,24 +37,16 @@
 
 
 /*
-	Important data from the USB spec (not interesting for drivers)
+ * Important data from the USB spec.
-*/
+ */
 
-struct memory_chunk
+struct usb_request_data {
-{
-	uint32 next_item;
-	uint32 physical;
-};
-
-
-struct usb_request_data
-{
 	uint8   RequestType;
 	uint8   Request;
 	uint16  Value;
 	uint16  Index;
 	uint16  Length;
-};
+} _PACKED;
 
 
 struct usb_isochronous_data {
@@ -65,8 +57,7 @@ struct usb_isochronous_data {
 };
 
 
-struct usb_hub_descriptor
+struct usb_hub_descriptor {
-{
 	uint8 length;
 	uint8 descriptor_type;
 	uint8 num_ports;